542 



PAGE 



optata, see Millardia. 



Oquirrh Range, Utah, Middle Cambrian localities 3296, 3c 371 



orbicularis, see Acrothele. 



Ordovician, depositions 91 



dolomite, influence of calcareous algae 92 



faunas, comparison, Middle Cambrian Trilobita 60 



genera of Ogygiocaringe, foreshadowed in Ogygopsis and Orria. . . . 376 



localities, China, C39, C53, C59, C64, and C65 25-29 



relation, Cambrian 41 



section. Upper Cambrian and Lower 55 



Ore Hill, Pennsylvania, Upper Cambrian locality 1076 392, 393 



orientalis, see Helcionella rtigosa, Huenella, Microdiscus, Micromitra 

 (Paterina) labradorica, Stenotheca rugosa, Syn- 

 trophia, and Yorkia. 

 ornatus, see Bathyuriscus. 



Orr formation, Utah, Middle Cambrian localities 30 I, 30y 374 



Upper Cambrian localities 15J, ist 185 



localities 3oh, 301, 30J 207 



Orria, new genus, described 379 



compared with Bathyuriscus (footnote) 379 



Bathyuriscus, Ogygopsis, and Ogygiocaris 380 



genotype, Orria elegans Walcott 380 



relation to Ogygopsis 380 



stratigraphic and geographic range 380 



suggests Ogygiocaris buchii (Brongniart) 380 



under Ogygiocarinae 375 



elegans, new species, described 381 



figured, pi. 66, figs. 2, 2a-b 454 



associated fauna, listed under Marjumia typa 402 



compared with Ogygopsis klotzi (Rominger) 377 



genotype of Orria 380 



listed 403 



orthia, see Syntrophia. 



Orthis, genus cited, Gottsche 7 



linnarssoni Kayser (=Eoorthis linnarssoni) , generic references... 15 

 identified, Carnegie Institution of Washington collection.... 6 



,sp., listed, Tsing-tshou-f u 11 



(Plectorthis) agreste (=Eoorthis agreste), generic references.... 15 



(Plectorthis) doris (^Eoorthis doris), gentric references 15 



(Plectorthis) kayseri (=Eoorthis kayseri), generic references.... 15 

 (Plectorthis) kichouensis (^=Eoorthis kichouensis) , generic refer- 

 ences 15 



(Plectorthis) linnarssoni (Kayser) Walcott (^Eoorthis linnars- 

 soni), generic references 15 



(Plectorthis) pagoda {=^Eoorthis pagoda), generic references.... 15 



Orthotheca and Hyolithes, discussed under Pteropoda 59 



cyrene Walcott, listed, upper Ch'au-mi-tien 68 



Shantung and Manchuria 70 



stratigraphic and geographic position 46 



